Well there's nothing the 7mm WSM can do better than the 7mm Rem Mag so to me it's a no brainer.
The Short and ultra short magnums have a "coll factor" about them but to me they are mostly a novelty.
Some guys want to go with the short actions for a perceived weight benefit but in truth you are just talking about a few ounces difference.
I shot the 7mm Rem Mag from about 1977 till I fell in love wit the 7mm STW in about 1990 and it is probably the most versatile caliber ever invented, for shooting everything from small varmints to the biggest game N. America has to offer with great ballistics and performance with very tolerable recoil.
Now I just do it a little bit faster with the STW... .